Mineral fibre products generally comprise man-made vitreous fibres (MMVF) such as, e.g., glass fibres, ceramic fibres, basalt fibres, slag wool, mineral wool and stone wool, which are bonded together by a cured thermoset polymeric binder material. For use as thermal or acoustical insulation products, bonded mineral fibre mats are generally produced by converting a melt made of suitable raw materials to fibres in conventional manner, for instance by a spinning cup process or by a cascade rotor process. The fibres are blown into a forming chamber and, while airborne and while still hot, are sprayed with a binder solution and randomly deposited as a mat or web onto a travelling conveyor. The fibre mat is then transferred to a curing oven where heated air is blown through the mat to cure the binder and rigidly bond the mineral fibres together.
In the past, the binder resins of choice have been phenol/formaldehyde resins which can be economically produced and can be extended with urea prior to use as a binder. However, the desire to minimize Volatile Organic Compound (VOC) emissions from products in conjunction with existing and proposed legislation directed to the lowering or elimination of formaldehyde have led to the development of formaldehyde-free binders such as, for instance, the binder compositions based on polycarboxy polymers and polyols, as disclosed in EP-A-583086, EP-A-990727 and U.S. Pat. No. 5,318,990.
Another group of non-phenol/formaldehyde binders for mineral fibres are the addition/elimination reaction products of aliphatic and/or aromatic anhyrides with alkanolamines, e.g., as disclosed in WO 99/36368, WO 01/05725, WO 01/96460, WO 02/06178, WO 2004/007615 and WO 2006/061249. These mineral fibre binders are water soluble and exhibit excellent binding properties in terms of curing speed and curing density. However, despite these disclosures, there is a continuing need for identifying new formaldehyde-free, curable aqueous compositions suitable for use as a binder for mineral fibre products.
A type of product suffering from similar environmental problems associated with conventional phenol/formaldehyde binders are growth substrates for plants which are based upon man-made vitreous fibres or other porous substrates; see, for instance, GB-A-1336426. These substrates may, e.g., be provided in the form of slabs, blocks, plugs or other coherent products or in the form of granulate.
Conventional plant growth products generally comprise a binder, often a phenol-formaldehyde resin or urea-formaldehyde resin, which provides integrity to the product. After application of the binder, the products are subjected to curing at high temperatures in a curing oven.
It is essential that these plant growth substrates are able to take up and hold water, and therefore a certain wettability is required. Phenol-formaldehyde resins, and to lesser degree urea-formaldehyde resins are, however, found to impart water repellency to mineral wool products and, therefore, it is well-known to include a wetting agent in the plant growth substrate in order to achieve the desired hydrophilicity and wettability; see, for instance, WO 92/04824 and WO 01/82683. Such wetting agents must exhibit good environmental compatibility, in particular, low phytotoxicity. Moreover, in view of the working conditions employed during production of the plant growth substrates, they must have good thermal stability and also provide products having proper wet and dry compression strength in addition to the desired water-uptake capacity and water retaining capacity.
However, over time conventional wetting agents often are washed out of the plant growth substrate leaving a product of insufficient wettability and water retaining capacity.